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PROFESSOR MATTEUCCl’S ELECTRO-PHYSIOLOGICAL RESEARCHES. 
The experiment consists in this : that after fifteen or twenty minutes of the passage 
of the current, that limb only which is traversed by the inverse current, that is to 
say, in a direction contrary to the ramification of the nerve, contracts at the opening 
of the circuit. 
When the frog is reduced to this state, if the nerve traversed by the inverse cur- 
rent is touched by a small portion of muscle, we see the limb instantly contract 
as if the circuit had been interrupted ; and in fact the current ceases to pass through 
the nerve and enters the muscle on account of the greater conductibility of the latter 
substance. 
I shall cite another experiment of the same kind. Having succeeded in modi- 
fying the excitability of the nerve by the passage of the current, as in the expe- 
riment just described, we can easily convince ourselves that this modification is 
confined to the exposed or isolated portion of the nerves. For if those portions of 
the nerves in both thighs, which had been previously buried in the muscles, be 
now laid bare, no alteration in their excitability is found to have occurred ; but the 
altered excitability is limited to the pelvic portions of the nerves previously exposed 
and traversed by the current. It is evident that if the nerve, buried among the 
muscles of the thigh, were traversed by the current as its exposed portion above is, 
the modification of the exeitability would extend through the whole length of the 
nerve. I repeat, therefore, once again, that when a muscular mass is traversed by 
an electric current, we are compelled to admit that no sensible quantity of that 
current is conducted by the nervous filament belonging to such muscle. 
Another subject of research which has greatly interested me, and the exposition 
of which will precede that of the experiments which form the principal subject of 
this memoir, relates to the influence which the integrity of the nervous system exer- 
cises on the excitability of the nerves. In other words, supposing that a certain 
contraction is produced in the limb of a frog by the passage of a constant electric 
current through its lumbar nerves, would that contraction remain the same, or would 
it be increased or diminished were the spinal marrow to be cut ? I had read in the 
‘Comptes Rendus’ of the Academy of Paris an experiment by M. Bois Seguard, 
from which one would be led to conclude that the section of the spinal marrow in- 
creased the excitability of the lumbar nerve, at least during a certain period of time. 
In order completely to satisfy myself on this point, which I consider as very im- 
portant with regard to the theory of nervous functions, I was obliged to operate with 
the greatest possible exactitude, and to measure in every instance the contractions 
excited. In order to this I employed an apparatus invented by M. Breguet, the de- 
scription of which I have given in my fourth memoir*. The results to be obtained 
from this apparatus are as exact as can be desired, provided the operation is carried on 
with sufficient patience, and that the necessary degree of practice has been acquired 
in the use of the machine. As it is necessary, in the first instance, that the current 
* Philosophical Transactions, 1846. 
